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An alternative clean regeneration method to calcination on special grade resins, i.e. Nafion, is introduced. The reactivation strategy makes use of advanced oxidation processes (Fenton and non-Fenton) to remove the organic deposits generated from sequential catalytic cycles. Hot water treatment was considered as a control case to evaluate the extraction capacity of water itself at the oxidative conditions. Advanced oxidation processes were effective in reactivating the Nafion SAC-13 resin, which also rendered a cleaner and more sustainable reactivation process. Beta zeolite was studied as model fouled system prior to the Nafion SAC-13. Even though zeolites are considered to be thermally stable, this approach can be used when a full preservation of the acid sites is required. As far as resin Nafion SAC-13 is concerned, organic species deposition was found to be responsible of a selective poisoning of the sulfonic groups in Nafion, with a consequent drop in catalytic activity of the octanoic acid esterification with methanol. The Nafion resin was reactivated either with H2O2 or with Fenton chemistry; the resin remained stable under these oxidative conditions, which is the benefit of the presented nonthermal methodologies as compared to calcination. The optimal method showed full recovery of the initial activity and 90% of the final conversion. This methodology seems attractive for a whole-range of organic catalytic reactions, including those related to biomass valorization, that require the use of highly acidic catalysts, such as acidic resins, in liquid phase reactions. |
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